BOSTON -- All season long, the Houston Rockets and NBA champion Golden State Warriors ran 1-2 in the Western Conference, eventually ending up in the conference finals with little resistance.

Over in the East, the Toronto Raptors charged to the top seed and appeared to be in good shape to represent the conference in the NBA Finals.

However, the Boston Celtics and Cleveland Cavaliers, the Nos. 2 and 4 seeds, respectively, overcame all kinds of adversity and open their second straight conference finals Sunday at TD Garden.

For the Celtics, the adversity started five minutes into the season when shiny new free agent Gordon Hayward went down with a season-ending injury. Charles Barkley declared "their season is over" on national television. Other injuries followed as rookie surprise Daniel Theis lost for the season and Kyrie Irving, acquired from the Cavs in a huge deal, was also lost -- both with knee surgery.

Valuable piece Marcus Smart went down late after right thumb surgery -- and the list went on and on -- but it never really stopped Brad Stevens' team.

"I think in the Toronto series, no disrespect to them, but watching film it just looked very easy at times," Morris said. "... There was no help, I didn't see no physicality. I didn't see any of that. I think that's something different we'll bring to the table."

The Cavs, looking for their fourth straight conference title behind LeBron James, never got anything out of the damaged Isaiah Thomas (hip) and wound up shipping Thomas and fellow former Celtic Jae Crowder out of town as part of a major overhaul at the trade deadline. They dropped to fourth in the conference as the Philadelphia 76ers ran off 16 straight wins at the end of the season.

They needed seven games to dispose of the Indiana Pacers and then rampaged through the Raptors in four straight.

James has been on a tear, averaging 34.3 points, 9.4 rebounds, 9.0 assists, 1.5 steals and 1.0 blocks as he seeks his eighth straight trip to the NBA Finals.

"Last year, we were a unique group. ... Guys that went out and obviously played hard every night," Celtics forward Al Horford said. "We're doing the same thing now, but with this group, we have more depth in those positions, suited more to guard LeBron. We have a lot more bodies to take on that challenge."

They will need them.

The absence of Hayward, Irving and others led to the emergence of Jayson Tatum, Terry Rozier and Jaylen Brown as stars. Smart has come back from his surgery to provide a significant spark. The Celtics needed seven games to oust the Milwaukee Bucks and five to beat Philadelphia.

They are 7-0 at home in the playoffs.

"A lot of people are saying, 'How can they succeed like this without Gordon Hayward?' I've heard that," James said. "He's been out since the first quarter of Game 1, so it's like, do we even know who they would have (become)? He's not even, like, been on the team. So we can talk from, like, potential, but he's been out since the first quarter of Game 1 in Cleveland.

"I get it with the Kyrie thing. He was obviously a teammate of mine for three years, and I know what he's capable of doing, but they got guys that's damn good no matter if they are young or not. They know how to play basketball and their coach has put them in position to succeed."

Tatum has a shot at history in this series. He has recorded seven straight 20-point games, tying him with Donovan Mitchell for the second-most all time among rookies. Lew Alcindor, then of the Milwaukee Bucks, holds the record with 10 in a row in 1970.

Shane Larkin, Boston's backup point guard, suffered a shoulder sprain running into a Joel Embiid pick and has hopes of returning some time during the series.

"It's still fresh; it's still sore," he said. "I can't really do much. It's frustrating, but I've got to keep staying positive, keep getting treatment and try to get back out there."

Horford has been a leader for Boston through the 12 playoff games, averaging 17.0 points, 8.7 rebounds, 3.3 assists, 1.2 steals and 1.3 blocks per game -- essentially doing everything for his team.

The Cavaliers went 2-1 against the Celtics during the regular season and are 9-3 at TD Garden over the last four seasons.